区域重力均衡异常和上地幔小尺度对流模型

REGIONAL GRAVITY ISOSTATIC ANOMALY AND SMALL SCALE CONVECTION MODEL IN UPPER MANTLE

假定区域重力均衡异常主要源于由上地幔小尺度热对流相应的物质的不均匀和由此对流动力效应而导致的边界形变，同时将上地幔模拟为一均匀的等粘滞系数的牛顿粘滞流体，其主要的热量来自下地幔．由此建立了以流体力学３个基本方程为基础的热对流模型，并讨论了低瑞利数状态下，以区域重力异常和上地幔小尺度对流相关方程为主要条件，上述方程的基本解．几种模拟重力均衡异常所对应的流场表明；区域重力均衡异常正异常中心对应于上地幔小尺度对流上升流，表现出地幔上隆；相反，负异常中心对应于对流下降流，表现出岩石层（地壳）向下弯曲．结合实际的地质构造形态和重力异常形态，这些结果将有利于对板块内部岩石层动力学的理解．

Assuming that regional gravity isostatic anomalies are distributed by the density heterogeneities connected with small-scale convection in the upper mantle and the boundary deformations, we establish a convection model in this paper, which is constrained on the regional isostatic gravity anomaly. The computation models show that a possitive center of isostatic gravity anomaly corresponds to a divergent zone of mantle flow and a negative center corresponds to a convergent zone. The convection patterns are stable at lower Rayleigh number regions up to about 1. 5 time the critical.